1. Field of the Invention
This invention relates to multipurpose oil-soluble additives for lubricating oils which have utility to impart to an oil when incorporated therein an improved viscosity index and/or sludge dispersancy and/or pour point depressancy and/or oxidation stability and/or metal-wear protection and to the preparation of such additives. Broadly, the novel additives are the reaction products of compounds containing nitrogen, oxygen, sulfur, boron and/or phosphorous with polymers prepared by electrophilic termination of an anion of an oxidized copolymer of ethylene and at least one C.sub.3 -C.sub.50 alpha monoolefin, e.g., propylene, which anion had been generated upon contact of the copolymer with a strong base such as butyllithium.
2. Description of the Prior Art
The literature abounds with discussions of multipurpose, i.e., multifunctional, viscosity index (V.I.) improvers usually containing nitrogen to enhance their dispersant activity including polymeric nitrile-containing substances as lubricating oil additives with detergent-dispersant and other properties.
The preparation of such multifunctional V.I. improving polymeric substances containing nitrogen according to the prior art included: free radical-grafting a hydroperoxidized ethylene copolymer with a polar vinylidene monomer, such as acrylonitrile (see U.S. Pat. No. 3,404,091); free radical-grafting an ester of an amino alcohol onto an oxidized interpolymer of ethylene and propylene (see U.S. Pat. No. 3,687,849); and, thermally reacting amines with an oxidized ethylene-propylene copolymer (see U.S. Pat. No. 3,864,268). Free radical grafting has certain disadvantages, including irreversible crosslinking of the copolymer and homopolymerization of monomeric components.
Another approach to preparing an oil-soluble nitrogenous ashless dispersant involves reacting an alkali metal salt of a long-chain ketone with acrylonitrile (see U.S. Pat. No. 3,565,803 and 3,723,501). Unfortunately, formation of the dialkyl ketone precursor is by ozonization which is an expensive and hazardous process involving dimethyl sulfide, an environmentally toxic agent.
Also taught as a multifunctional additive for lubricating oils is the anionic-graft polymer of a lithiated ethylene-propylene-hexadiene terpolymer with an amino methacrylate monomer (see U.S. Pat. No. 3,879,304).